The present invention relates to a display controlling apparatus suitable for use in a reproducing apparatus for reproducing a CD-ROM for example in the XA format.
A video signal is intrinsically an analog signal and has substantially infinite number of gradations (stepless gradation). Therefore, when a circuit for processing a video signal is formed of an analog circuit, the image can be displayed substantially in stepless gradation and the image obtained is relatively easy to see. However, with information processing apparatuses such as personal computers, it is, often the case that the circuit for processing the video signal is formed of a digital circuit. In such case, the image is displayed with a predetermined number (finite number) of gradations.
In dividing brightness of a video signal into a predetermined number (finite number) of gradations, it has conventionally been practiced to divide it in a linear manner. Namely, the brightness has been divided into even ranges of gradation. As a result, there has been a problem that pixels concentrate in narrow ranges of gradation and, hence, the image becomes difficult to see.
The present invention was made in view of the above situation and it is an object of the present invention to achieve gradation conversion such that an image which is easier to see is obtained.
The display controlling apparatus according to the present invention comprises a D-RAM 97 as data storage means for storing video data corresponding to an image to be displayed, an interface LSI 95 as gradation conversion means for converting brightness of video data into a predetermined number of gradations in a nonlinear manner, and an LCD/CRT controller 94 as output means for outputting video data converted by the interface LSI 95 so as to have a predetermined number of gradations.
In the display controlling apparatus with the above described arrangement, video data stored in the D-RAM 97 is converted in a nonlinear manner into data with a predetermined number of gradations. Accordingly, pixels are scatteredly distributed over wider ranges of gradations and, hence, an image which is easier to see can be obtained.
Further, according to the method for gradation conversion with the above described arrangement, color data is converted into luminance data and the luminance data is converted in a nonlinear manner into data with a predetermined number of gradations. Accordingly, a color image can be simply converted to a monochromatic image which is easier to see.